Insulated sucker rod and tubing to prevent electrolysis and corrosion



UCL 5, 1954 s. M. HoLcoMBE INSULATED SUCKER ROD AND TUBING TO PREVENTELECTROLYSIS AND CORROSION Filed Aug. 28, 1950 Z. /f /0 2 )0MM w wazf1/p. f Ymo .M VHN 0 Z. m f5 M m i l l l i i i I l l l I I Illllllllllllllllllll li l W M m .0 n, .b Z0, 8

Patented Oct. 5, 1954 UNITED STATES PATENT OFFICE INSULATED SUCKER RODAND TUBING-T0 y"PREVENT ELECTROLYSIS AND CORROSION 3 Claims.

This invention relates to partsin an oil well subject to corrosion andelectrolytic action ot the well fluids and particularly to the tubingand sucker rods oi a well. It is -knownthat when wells produce uidscontaining electrolytic and corrosive elements such as salts, sulphurdioxide, and hydrogen sulphide, the rods and tubing are of relativelyshort'life and are constantly subject to failure. When such elements arepresent in the well fluids, electrolytic and corrosive action takesplace at the more vulnerable areas such as the joints and particularlythe threads thereof. Also rubbing or the rods on the tubing providespoints where the electrolytic action concentrates. Consequently, stress.in the rod-s at these points causes them to give awayin operation andresults in expensive vfishing jobs.

The objects of the present invention are thereiore to protect the tubingand sucker rods by substantially the sucker rods and tubing; to providefor the maintenance of tight joints and thereby prevent contact of thewell iiuids with the threads; to provi le thev sucker rod string `withinsulating couplings; to provide selected lcouplings with guides toprevent Contact of the rodswith-the tubing; to provide the tubing and/orsucker rods with an electrically insulating covering or skin whereby thesucker rods may be vmanufactured from the tougher butmore easilyattacked metals; to provide insulating guides having flow passagewaysthrough which the Well iiuids pass the couplings with a minimum ofresistance to the ilow and yet provide ample `bearing contact of theinsulating material with the Wall of the tubing, and to dampenvibrations of the rods.

in accomplishing these vand other objects of the invention ashereinafter pointed out, I have provided improved structure, thepreferred form oi which is illustrated in the accompanying drawingswherein:

Fig. l is a longitudinal section through a string of Well tubing andsucker rods embodying the features of the present invention.

Fig. 2 is an enlarged longitudinal section through the tubing and one ofthe coupling members particularly illustrating the insulating guidethereon.

Fig. 3 is a cross-section on'the line 3--3 of Fig. 2.

Fig. 4 is a section through one4 of the standard sucker rod couplingsmodied in'accordance with the present invention.

Fig. 5 isa cross-sectionthroughone of the rods lon the line 5-5 vofFig-'4.

eliminating electrolysis between J Fig. 6 is an enlarged section throughone oi' the tubing couplings.

Fig. 7 is a fragmentary section through one of the sucker rod couplings.

Referring more in detail to the drawings:

l designates a bore hole of a vwell extending from the top of theground'to a formation 2 producing, for example, petroleum oil. Extendingdownwardly in the bore hole is a tubing il carrying a pump L3 and astrainer section 5 .through which the oil is admitted to the pump. Thepump t includes a standing valve 6 seated in the lower end of thexpumpcylinder "i, and reciproca-ble in the cylinder. is a piston B carrying aWorking valve 9 to which astring of sucker rods I@ is connected.Thestring of sucker rods continue upwardly through the tubing forreciproca-tion above ground by ymeans of a suitable pumping jack (notshown). lThe tubing Si is composed of a series of pipe `sections ilinterconnected by couplings l2 having internal threads I3 engagingexternal threads-lli on the adjacent ends of the pipe sections. Thesucker rod string includes plurality of sucker rods l5 having rodlikebody portions lli formed at the ends to provide upsets ll and I8 on therespective sides of wrench-engaging faces I9. Also formed on the ends ofthe sucker rods are shoulders 2li and tapered pins 2| having externalthreads 22 which engage in the threaded-sockets or boxes 23 and it atthe respective ends of rod couplings 25. The threaded sockets ror boxesmay lbe formed at the ends of a continuoous bore 2B if desired. Thestrainer 5 usually consists of one or more sections of pipe havingperiorations for admitting the well fluids to the pump. VThe structurethus far disclosed is conventional of sucker rods and tubing used in thepumping of oil wells. Usually crude petroleum contains corrosive andelectrolytic fluids that attack the 'metals of the sucker rods and.tubing and cause fatigue failures, particularly at` the threaded jointsof the couplings.

The electrolyticaction produced by the presence of electrolytescontained with the petroleum causes electric vcurrents to flow from therods to the tubing and results in rapid pitting and reduction of thecross-'sectional area ofthe' rods so that the rods are subject tofailure under stress and especially repetitions of'stresses as occur inloading and unloading of the rods incidental to reciprocationv thereof.

As labove pointed'out, suchA Wellsv are usually vout-'of plumb'due-.tothe impossibility of drilling 11a `straight .'.bore :hole i with fthe-(result i that the string of sucker rods rubs upon the tubing atvarious points throughout the depth of the well. This rubbing actionduring reciprocation of the rods effects rapid wear of the tubing androds which also adds to the hazard and increases fatigue failurespromoted by electrolytic and corrosive effects of the fluid.

In carrying out the present invention, I have provided a tubing andsocker rod, tubing and coupling construction which eliminates the abovedifficulties by preventing any direct contact of the metal with the wellliquids. This is eiected by provision of the rods, tubing, and couplingswith an electrically insulating coating or skin to prevent passage ofthe electrolytic currents that cause deterioration. Each section of pipecomposing the string of tubing is provided with a lining-like coating 21on the inner surface and extending the full length thereof. The coatingmay be formed of any suitable insulating material that is resistant toaction of the well liquids. For example, one of the synthetic rubberscommonly known as neoprene or the equivalent which is applied to theinner surface by dipping the sections of pipe into a liquid body ofself-vulcanizing synthetic rubber.

The sections of sucker rod are similarly coated as indicated at 28 withthe exception of the threads the pins 2l.

The standard sucker rod couplings are also preferably covered with asimilar coating 29. Therefore, when the sections of sucker rods areconnected together by couplings, the entire surface of the entire stringis electrically insulated along the entire length thereof to preventpassage of electrolytic currents from the rods through the electrolyticcontent of the well fluids to the tubing as long as the pins 22 andboxes are tightly engaged. To assure tight connections of the threads,the bore of the couplings are closed midway the length thereof by plugs3B which are threaded into the bore and form backing for blocks 3| ofrubber or preferably synthetic resilient material. The blocks are ofample thickness relatively to the depths of the sockets and length ofthe pins so that when the pins of the rods are completely engaged withinthe sockets of the couplings, the resilient material is compressed toprovide a resistance to backward turning of the rods and thereby assuresuiciently tight joints to prevent intrusion of the well liquids. Thematerial from which the blocks are formed is of suiiicient resiliency sothat when the rods are to be uncoupled, they will yield suiciently topermit turning of the rods. To prevent the end of the rod from tearingthe surface of the blocks, suitable washers 32 may be insertedtherebetween as best shown in Fig. '7.

The ends of the pipe sections Il when turned up tightly within thecouplings leave gaps 33 therebetween which ordinarily expose the threadsI3 to the action of the well iiuids, but to overcome this diificultyeach coupling is provided with a ring 31% of the resilient insulatingmaterial and which is compressed between the ends of the adjacent pipesections to assure leak-tight joints therebetween. The rings 34 alsoassure resistance to backward turning of the pipe sections.

In order to prevent contact of the sucker rods on the tubing and avoiddestruction of the resilient insulating coatings, special guidecouplings 35 are provided at spaced intervals along the length of thesucker rods. These couplings may be substituted for the couplingsillustrated in Fig. 4 at the points at which the guides are necessary.The couplings include a relatively short length of sucker rod section 36having box ends 3l and 38 provided with internal threads 39 and 40 toreceive the pins on the ends of the adjacent sucker rods. The sucker rodsections 3S have the usual wrench engaging faces lil and collar-likeupsets 42. Mounted on the body of the coupling rodV sections aresubstantially cylindrical guides d3 which are preferably molded thereonand retained from longitudinal movement by the upsets 42 and key slots44 that connect with an axial channel 45 through which the materialflows to the socket ends to provide the resilient abutments 46 and 4lfor the pins of the adjacent rod sections. The guides are preferably ofslightly smaller diarneter than the tubing to allow free movement of therods and the ends are rounded as at 48 to assure easy entrance thereofinto the open upper end of the well tubing as when running the suckerrods into the well. In order to permit free passage of the well liquid,the circumferences of the guides are provided with intersecting flowpassages 49 and 49' that extend in criss-crossing relation from one endof the guide to the other as best shown in Fig. l. With thisarrangement, diamond shaped islands 5B are formed between thepassageways which give ample contact surface 5! with the tubing toassure su'icient support of the tubing to prevent too rapid wear of therubbing surfaces.

The screen section may be coated on the inner and outer sides with asynthetic rubber as indi'- cated at 52 and 53 and the openings may beprovided with magnesium inserts 54 having ports 55.

In using the structure as aboveV described, the tubing and sucker rodsare run into the well in 'the same manner as conventional tubing andsucker rods so that when the elements are in place and the pump inoperation, the metal of the sucker rods and tubing are completelyinsulated by the coatings and the sucker rod and tubing sections areretained in tight relation with their couplings by the resilient actionof the rubber abutting blocks. During reciprocation of the rods, theresilient bodies 43 of the guide couplings move in sliding contact tohold the rods concentric in the tubing.

It is thus obvious that any electric currents that may be carried by therods are prevented from discharge by electrolytic `action to the tubing,consequently, the rods are free of the usual deteriorating effects ofsuch currents and will operate for long periods without the customaryhazards usually caused by corrosion and electrolysis.

From the foregoing, it is obvious that I have provided sucker rods andtubing which are amply protected from corrosion and electrolysisordinarily produced by well nuids and that the threads are kept in tightcondition so as to prevent intrusion of the well uids at these points.

What I claim and desire to secure by Letters Patent is:

1. A coupling for sucker rods having ends provided with internallythreaded sockets, coaxial cylindrical body of electrically insulatingniaterial exteriorly encircling the coupling and hav ing an exteriorsurface provided with ow pas sages, and resilient abutment means in saidsockets, said abutment means being integral, with the insulating body.

2. A coupling for sucker rods comprising a rod-like body havinginternally threaded sockets on the ends thereof with said socketsconnected by a coaxial bore through the body, a resilient material insaid coaxial bore and forming bottoms for said sockets, said rod likebody having a radial opening in connection. with said bore and acylindrical body of said material having a portion extending through theradial opening and integral With the material in said bore andsurrounding the rod-like body.

3. A pony rod comprising a member having a rod like body portionprovided with internally threaded sockets on the ends thereof and havingan axial bore interconnecting said sockets, said rod like body portionof the sucker rod having spaced apart annular upsets and having slotlike openings extending through the said bore intermediate said upsets,a resilient insulating material encircling the rod like body and llingthe bore for forming resilient 'bottoms in said sockets, said materialextending through the 6 slot like openings for integrally connecting theencircling material with the material in the bore.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,576,767 Loomis Mar. 16, 1926 '1,804,078 Baden May 5, 19311,814,183 Patterson July 14, 1931 2,063,863 Zimmerman et al. Dec. 8,1936 2,096,359 Hawthorn Oct. 19, 1937 2,166,116 Bettis July 1S, 19392,175,770 Dodson Oct. 10, 1939 2,178,931 Crites Nov. 7, 1939 2,181,361Bean Nov. 28, 1939 2,337,711 Crake Dec. 28, 1943

